Lesson 5 Muscle Physiology

Question 1

What is the epimysium?

Answer 1

connective tissue that surrounds the muscle

Question 2

What is a muscle fascicle?

Answer 2

bundles of muscle fibers surrounded by perimysium

Question 3

What does perimysium surround and what runs under this layer?

Answer 3

muscle fascicles

nerves and vasculature run through this area

Question 4

What connective tissue surrounds each individual muscle fiber?

Answer 4

endomysium

Question 5

What are the thick and thin filaments of muscle fibers?

Answer 5

thick: myosin

thin: actin, tropomyosin, troponin

Question 6

What is the order from deepest to outermost layers of muscle?

Answer 6

fibers > endomysium > fascicles > perimysium > epimysium

Question 7

What are the structure proteins in muscle fibers?

Answer 7

titin, desmin, and dystrophin

Question 8

What is the z line of a sarcomere?

Answer 8

provides stability to muscle fibers, connecting adjacent actin filaments

Question 9

What is an M band of the sarcomere?

Answer 9

bisects the central portion of the sarcomere, providing support for the myosin filaments, middle

Question 10

What is the I band?

Answer 10

location of only thin filaments

Question 11

What is the A band?

Answer 11

where actin and myosin overlap

Question 12

What is the H zone?

Answer 12

only thick filament

Question 13

What does the sliding filament theory explain?

Answer 13

how muscles contract to produce force

Question 14

What happens during the cross bridge formation of sliding filament theory?

Answer 14

calcium binds to troponin, shifting tropomyosin which exposes myosin binding sites

myosin binds to actin

Question 15

What happens during the power stroke of sliding filament theory?

Answer 15

myosin head pivots and pulls actin filament towards M-line, causing a contraction

Question 16

What is released after the power stroke?

Answer 16

ADP and phosphate after breaking down ATP

Question 17

What happens during cross bridge detachment of sliding filament theory?

Answer 17

atp binds to myosin to cause release from actin

Question 18

What happens during the reactivation of myosin step of the sliding filament theory?

Answer 18

ATP hydrolyzed into ADP and P to reset myosin head

Question 19

What is excitation-contraction coupling steps?

Answer 19

1. action potential generated and sent down T-tubules, due to ACh release
2. action potential triggers calcium release into sarcoplasmic reticulum
3. calcium binds to troponin
4. contraction
5. removal of calcium
6. tropomyosin block restored

Question 20

What is oxidative capacity?

Answer 20

a property that reflects a muscle fibers ability to generate ATP from aerobic metabolism

Question 21

What determines a muscle fibers oxidative capacity?

Answer 21

mitochondria content, amount of myoglobin, and capillary density

Question 22

What is myosin isoform?

Answer 22

variation of myosin heavy chain or myosin light chain protein that determines speed of contractions

Question 23

What does high ATPase activity mean?

Answer 23

faster speed of contractions

Question 24

How does the amount of contractile proteins influence force?

Answer 24

the larger number of proteins, the larger the force of contraction

Question 25

What is the equation of maximal power output?

Answer 25

power = force x speed of contraction

Question 26

What is efficiency of contraction?

Answer 26

amount of ATP used per unit of power generated

Question 27

What is a type 1 muscle fiber?

Answer 27

slow twitch fiber

Question 28

What are the properties of a type 1 or slow twitch fiber?

Answer 28

- high oxidative capacity and resistant to fatigue - slow speed of contraction, less force - most efficient

Question 29

What are type 2x fibers?

Answer 29

fast twitch or fast glycolytic fibers

Question 30

What are the properties of type 2x or fast twitch muscle fibers?

Answer 30

- fastest contraction - many glycolytic enzymes - similar force to 2a - highest power output

Question 31

What are type 2a fibers?

Answer 31

intermediate or fast oxidative glycolytic fibers

Question 32

What are the properties of type 2a fibers?

Answer 32

properties between type 1 and 2x

Question 33

What are the most abundant fiber types in sedentary people?

Answer 33

50% type 1

Question 34

What are the most abundant muscle fibers in power athletes?

Answer 34

type 2

Question 35

What muscle fiber type do endurance athletes mostly have?

Answer 35

type 1 fibers

Question 36

What fiber type do small motor neurons tend to innervate?

Answer 36

type 1 fibers, able to coordinate movement

Question 37

What fiber type do large motor neurons tend to innervate?

Answer 37

type 2, largest = type 2x, less coordination

Question 38

When motor neurons generate an action potential, this causes all muscle fibers it innervates to contract at once, resulting in a muscle _______

Answer 38

twitch

Question 39

What is tetanus?

Answer 39

the act of muscle twitches summating and reaching a peak force

Question 40

What is rate coding?

Answer 40

the process by which a motor neuron can increase fore output by increasing its discharge rate

Question 41

What is recruitment?

Answer 41

process by the nervous system causes more motor neurons to fire to cause more muscle fibers to contract

Question 42

What is orderly recruitment?

Answer 42

smaller motor units recruited first then larger motor units

Question 43

What is the fast fatiguable twitch type for a muscle fiber?

Answer 43

generate force rapidly and produce high force but easily fatigued and force declines rapidly

Question 44

What is the fast fatigue resistant twitch type of muscle fibers?

Answer 44

fast force generation, moderate force, moderate resistance to fatigue

Question 45

What is a slow twitch type for muscle fibers?

Answer 45

slow force generation, low force, high resistance to fatigue

Question 46

How does force generation differ by sex?

Answer 46

it doesn't

Question 47

How does force generation change with age?

Answer 47

mass decrease due to decrease in size of type 2x fibers